[Qemu-devel] [PATCH 1/3] vfio: cleanup vfio_get_device error path, remove vfio_populate_device callback

[Paolo Bonzini]

With the next patch vfio_put_base_device will be called unconditionally at
instance_finalize time, which will mean calling it twice if vfio_populate_device
fails.  This works, but it is slightly harder to follow.

Change vfio_get_device to not touch the vbasedev struct until it will
definitely succeed, moving the vfio_populate_device call back to vfio-pci.
This way, vfio_put_base_device will only be called once and only on
non-error paths.

Cc: Alex Williamson <alex.william...@redhat.com>
Signed-off-by: Paolo Bonzini <pbonz...@redhat.com>
---
 hw/vfio/common.c              | 31 ++++++++++++-------------------
 hw/vfio/pci.c                 | 11 +++++++----
 include/hw/vfio/vfio-common.h |  1 -
 3 files changed, 19 insertions(+), 24 deletions(-)

diff --git a/hw/vfio/common.c b/hw/vfio/common.c
index cf483ff..242b71d 100644
--- a/hw/vfio/common.c
+++ b/hw/vfio/common.c
@@ -867,27 +867,28 @@ int vfio_get_device(VFIOGroup *group, const char *name,
                        VFIODevice *vbasedev)
 {
     struct vfio_device_info dev_info = { .argsz = sizeof(dev_info) };
-    int ret;
+    int ret, fd;
 
-    ret = ioctl(group->fd, VFIO_GROUP_GET_DEVICE_FD, name);
-    if (ret < 0) {
+    fd = ioctl(group->fd, VFIO_GROUP_GET_DEVICE_FD, name);
+    if (fd < 0) {
         error_report("vfio: error getting device %s from group %d: %m",
                      name, group->groupid);
         error_printf("Verify all devices in group %d are bound to vfio-<bus> "
                      "or pci-stub and not already in use\n", group->groupid);
-        return ret;
+        return fd;
     }
 
-    vbasedev->fd = ret;
-    vbasedev->group = group;
-    QLIST_INSERT_HEAD(&group->device_list, vbasedev, next);
-
-    ret = ioctl(vbasedev->fd, VFIO_DEVICE_GET_INFO, &dev_info);
+    ret = ioctl(fd, VFIO_DEVICE_GET_INFO, &dev_info);
     if (ret) {
         error_report("vfio: error getting device info: %m");
-        goto error;
+        close(fd);
+        return ret;
     }
 
+    vbasedev->fd = fd;
+    vbasedev->group = group;
+    QLIST_INSERT_HEAD(&group->device_list, vbasedev, next);
+
     vbasedev->num_irqs = dev_info.num_irqs;
     vbasedev->num_regions = dev_info.num_regions;
     vbasedev->flags = dev_info.flags;
@@ -896,20 +897,12 @@ int vfio_get_device(VFIOGroup *group, const char *name,
                           dev_info.num_irqs);
 
     vbasedev->reset_works = !!(dev_info.flags & VFIO_DEVICE_FLAGS_RESET);
-
-    ret = vbasedev->ops->vfio_populate_device(vbasedev);
-
-error:
-    if (ret) {
-        vfio_put_base_device(vbasedev);
-    }
-    return ret;
+    return 0;
 }
 
 void vfio_put_base_device(VFIODevice *vbasedev)
 {
     QLIST_REMOVE(vbasedev, next);
-    vbasedev->group = NULL;
     trace_vfio_put_base_device(vbasedev->fd);
     close(vbasedev->fd);
 }
diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
index 014a92c..2f5f718 100644
--- a/hw/vfio/pci.c
+++ b/hw/vfio/pci.c
@@ -195,7 +195,6 @@ static uint32_t vfio_pci_read_config(PCIDevice *pdev, 
uint32_t addr, int len);
 static void vfio_pci_write_config(PCIDevice *pdev, uint32_t addr,
                                   uint32_t val, int len);
 static void vfio_mmap_set_enabled(VFIOPCIDevice *vdev, bool enabled);
-static int vfio_populate_device(VFIODevice *vbasedev);
 
 /*
  * Disabling BAR mmaping can be slow, but toggling it around INTx can
@@ -2934,12 +2933,11 @@ static VFIODeviceOps vfio_pci_ops = {
     .vfio_compute_needs_reset = vfio_pci_compute_needs_reset,
     .vfio_hot_reset_multi = vfio_pci_hot_reset_multi,
     .vfio_eoi = vfio_eoi,
-    .vfio_populate_device = vfio_populate_device,
 };
 
-static int vfio_populate_device(VFIODevice *vbasedev)
+static int vfio_pci_populate_device(VFIOPCIDevice *vdev)
 {
-    VFIOPCIDevice *vdev = container_of(vbasedev, VFIOPCIDevice, vbasedev);
+    VFIODevice *vbasedev = &vdev->vbasedev;
     struct vfio_region_info reg_info = { .argsz = sizeof(reg_info) };
     struct vfio_irq_info irq_info = { .argsz = sizeof(irq_info) };
     int i, ret = -1;
@@ -3247,6 +3245,11 @@ static int vfio_initfn(PCIDevice *pdev)
         return ret;
     }
 
+    ret = vfio_pci_populate_device(vdev);
+    if (ret) {
+        return ret;
+    }
+
     /* Get a copy of config space */
     ret = pread(vdev->vbasedev.fd, vdev->pdev.config,
                 MIN(pci_config_size(&vdev->pdev), vdev->config_size),
diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h
index 1d5bfe8..5f3679b 100644
--- a/include/hw/vfio/vfio-common.h
+++ b/include/hw/vfio/vfio-common.h
@@ -112,7 +112,6 @@ struct VFIODeviceOps {
     void (*vfio_compute_needs_reset)(VFIODevice *vdev);
     int (*vfio_hot_reset_multi)(VFIODevice *vdev);
     void (*vfio_eoi)(VFIODevice *vdev);
-    int (*vfio_populate_device)(VFIODevice *vdev);
 };
 
 typedef struct VFIOGroup {
-- 
1.8.3.1